Picture Archiving and Communications Systems (PACS) consist of various components to facilitate the management of images from various imaging modalities. It is therefore necessary to efficiently distribute medical images to various users. Pre-fetching and auto-routing are used to predict when an image will be accessed and to therefore place it in a cache or directly at the station where it is expected to be viewed, with the aim of cutting down wait time for an end user requiring a view of a particular image. Many attempts to reduce waiting times for image retrieval have been made.
For example, U.S. Pat. No. 6,574,629 to Cooke, Jr. et al. discloses a PACS that routes relevant prior studies to a reviewing station in contemplation of a scheduled event through pre-fetching. Pre-fetching rules, used to determine which prior studies on the PACS should be retrieved, are stored in memory and may be set and modified by the user. The studies are then placed into an archive station cache and routed to the appropriate station automatically.
Okura et al. (“An inductive Method for Automatic Generation of Referring Physician Prefetch Rules for PACS,” J. of Digital Imaging, pp. 226-231, Vol. 15, No. 4, December 2002), discloses an inductive method to generate pre-fetching rules based on practical data from a hospital (e.g. examination histories, previous images requests, etc.) by employing a decision tree algorithm. This avoids the pre-fetching of unnecessary data.
However, since these systems are designed to pre-fetch full fidelity image data, they introduce significant system load since in most applications prior exams do not need to be full fidelity. Also, these systems do not allow for optimization of data traffic across networks and between devices, or for optimization of the size and resolution of image data. As a result, these systems do not adequately address waiting times in the display of images.